REXEC(3)

✨ REXEC ✨ (the rexec man page, section 3, rexec 1.2 bestie 💖)

💫 NAME 💫

nfstest.rexec — the Remote procedure module 🫶

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🌸 DESCRIPTION 🌸

Okay so picture this: you've got a whole lil toolbox for running a huge range of commands, statements, expressions or functions over on a remote host. How? By running a server process on that remote host that just... serves your requests without disconnecting. Iconic behavior honestly. ✨

The way that matters is: it lets you do a whole sequence of operations remotely and not lose state. Like, you could open a file remotely, go do a bunch of other stuff, and then write to that same still-open file without opening it all over again. No re-opening, no drama. 💅

The remote server can also run as a different user by using the sudo option and sending seteuid. And it can run locally too — using fork when it's running as the same user, or using the shell when the sudo option is in play. Versatile queen. 👑

⚠️ Real talk though: to use this module, your user id has to be able to ssh to the remote host without needing a password. No password, no vibes. Periodt.

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🎀 CLASSES 🎀

🌈 class RemoteServer(builtins.object)

✨ Methods defined here:

• __del__(self) — the Destructor 🪦
• __init__(self, port, logfile=None) — Remote procedure server
• log(self, msg) — write message to log file 📝
• start(self)

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🦋 class Rexec(baseobj.BaseObj)

Rexec object 🫧

Rexec() -> New remote procedure object

Arguments:

• servername — name or IP address of remote server
• logfile — name of logfile to create on remote server
• sudo — run remote server as root

Usage:

from nfstest.rexec import Rexec

# Function to be defined at remote host
def add_one(n):
    return n + 1

# Function to be defined at remote host
def get_time(delay=0):
    time.sleep(delay)
    return time.time()

# Create remote procedure object
x = Rexec("192.168.0.85")

# Define function at remote host
x.rcode(add_one)

# Evaluate the expression calling add_one()
out = x.reval("add_one(67)")

# Run the function with the given argument
out = x.run("add_one", 7)

# Run built-in functions
import time
out = x.run(time.time)

# Import libraries and symbols
x.rimport("time", ["sleep"])
x.run("sleep", 2)

# Define function at remote host -- since function uses the
# time module, this module must be first imported
x.rimport("time")
x.rcode(get_time)

# Evaluate the expression calling get_time()
out = x.reval("get_time()")

# Run the function with the given argument
out = x.run("get_time", 10)

# Open file on remote host
fd = x.run(os.open, "/tmp/testfile", os.O_WRONLY|os.O_CREAT|os.O_TRUNC)
count = x.run(os.write, fd, "hello there
       ")
x.run(os.close, fd)

# Use of positional arguments
out = x.run("get_time", 2)

# Use of named arguments
out = x.run("get_time", delay=2)

# Use of NOWAIT option for long running functions so other things
# can be done while waiting
x.run("get_time", 2, NOWAIT=True)
while True:
    # Poll every 0.1 secs to see if function has finished
    if x.poll(0.1):
        # Get results
        out = x.results()
        break

# Create remote procedure object as a different user
# First, run the remote server as root
x = Rexec("192.168.0.85", sudo=True)
# Then set the effective user id
x.run(os.seteuid, 1000)

🌟 Methods defined here:

• __del__(self) — Destructor 🪦
• __init__(self, servername=None, logfile=None, sudo=False, timeout=30.0) — Constructor

Initialize object's private data. 💾

• servername — host name or IP address of host where remote server will run [Default: None (run locally)]
• logfile — pathname of log file to be created on remote host [Default: None]
• sudo — run remote procedure server as root [Default: False]
• timeout — timeout for synchronous calls [Default: 30.0]

• close(self) — close connection to remote server 👋
• poll(self, timeout=0) — return whether there is any data available to be read
  • timeout — maximum time in seconds to block, if timeout is None then an infinite timeout is used ⏳
• rcode(self, code) — define function on remote server
• results(self, xid=None) — return pending results
• reval(self, expr) — evaluate expression on remote server 🧮
• rexec(self, expr) — execute statement on remote server
• rimport(self, module, symbols=[]) — import module on remote server 📦
  • module — module to import in the remote server
  • symbols — if given, import only these symbols from the module
• run(self, *kwts, **kwds) — run function on remote server 🏃♀️

The first positional argument is the function to be executed. All other positional arguments and any named arguments are treated as arguments to the function.

• wait(self, objlist=None, timeout=0) — return a list of Rexec objects where data is available to be read
  • objlist — list of Rexec objects to poll, if not given use current object
  • timeout — maximum time in seconds to block, if timeout is None then an infinite timeout is used ⏳

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👀 SEE ALSO 👀

baseobj(3)

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💀 BUGS 💀

No known bugs. (Not a single one, bestie — we ate and left no crumbs. 🔥)

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👑 AUTHOR 👑

Jorge Mora (mora@netapp.com)

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And that's the whole page, fr fr 🫶 This was NFStest 3.2, dated 21 March 2023 — go forth and remote-procedure slay 💅✨